Multi-stage centrifugal pump

ABSTRACT

A MULTI-STAGE CENTRIFUGAL PUMP OF SIMPLE COMPACT DESIGN UTILIZING A PLURALITY OF PAIRS OF DIAMETRICALLY ARRANGED VOLUTE PASSAGES IN THE SAME PLANE AND HYDRAULICALLY BALANCED. EACH PASSAGE OF ONE PAIR COMMUNICATES AT ITS INNER END WITH THE INLET EYE OF THE IMPELLER DISC AND AT ITS OUTER END WITH THE IMPELLER CHAMBER AT BOTH SIDES OF THE IMPELLER DISC. EACH PASSAGE OF THE OTHER PAIR COMMUNICATES AT ITS INNER END WITH THE IMPELLER CHAMBER ON BOTH SIDES OF THE IMPELLER DISC AND AT ITS OUTER END THROUGH A SLOT IN THE RIM OF THE IMPELLER DISC WITH AN ANNULAR DISCHARGE CHAMBER, OUT OF WHICH OPENS THE OUTLET PORT. TWO DIFFUSER RINGS ARE SUPPORTED ON THE PUMP HOUSING IN COAXIAL RELATION TO AND ON OPPOSITE SIDES OF THE IMPELLER DISC AND ENGAGE THE OPPOSITE FACES OF THE IMPELLER DISC IN FREE-RUNNING CONTACT BETWEEN THE DISCHARGES FROM THE FIRST STAGE VOLUTE PASSAGES AND THE INLETS FOR THE SECOND STAGE VOLUTE PASSAGES.

Jan. 19; 1971 E. A. HOULE 3,556,671

MULTI STAGE CENTRIFUGAL PUMP Filed May 28, 1969 2 Sheets-Sheet 1 INVENTOR. ERNEST ARMAND HOULE AT TQRNEY Jan. 19, 1971 E. A; HOULE I MULTI-STAGEbENTRIFUGAL PUMP 2 Sheets-Sheet 2 Filed May 28, 1969 'INVENTOR. ERNEST ARMAND HOULE BY M.

ATTORNEY United States Patent US. Cl. 41598 Claims ABSTRACT OF THE DISCLOSURE A multi-stage centrifugal pump of simple compact design utilizing a plurality of pairs of diametrically arranged volute pasages in the same plane and hydraulically balanced. Each passage of one pair communicates at its inner end with the inlet eye of the impeller disc and at its outer end with the impeller chamber at both sides of the impeller disc. Each passage of the other pair communicates at its inner end with the impeller chamber on both sides of the impeller disc and at its outer end through a slot in the rim of the impeller disc with an annular discharge chamber, out of which opens the outlet port. Two diffuser rings are supported on the pump housing in coaxial relation to and on opposite sides of the impeller disc and engage the opposite faces of the impeller disc in free-running contact between the discharges from the first stage volute passages and the inlets for the second stage volute passages.

BACKGROUND OF THE INVENTION Multi-stage centrifugal pumps heretofore known utilize a plurality of separate coaxially related impeller discs serially related in such manner that the discharge one stage impeller supplies the inlet for a succeeding stage impeller. Such construction necessitates pump housing of corresponding length to accommodate the multiple impeller stages. Where space limitations and weight are a factor, such multi-stage multiple impeller centrifugal pumps have certain disadvantages. Accordingly, it is a desirable objective of the present invention to provide a simple compact design of multi-stage pump requiring only a single impeller disc, with the consequent advantages obtained of minimal housing length and weight.

SUMMARY OF THE INVENTION The embodiment of the invention described herein is a multi-stage centrifugal pump which obviates the necessity for multiple impeller discs and provides a plurality of stages arranged in a single impeller disc so as to impart hydraulic balance thereto. A single impeller disc carried in overhung relation to the end of a drive shaft is provided with two diametrically arranged volute passages, the inner ends of which are open to the eye of the impeller to which liquid is supplied from the pump inlet. The outer ends of these passages are open, respectively, via a corresponding axial through port to the impeller chamber at both sides of the impeller disc. Additionally, the impeller disc has two diametrical volute passages arranged in quadrature to the aforesaid two volue passages. The inner ends of the latter passages are open to both sides of the impeller disc, via respective axial through ports, and the outer ends of the latter passages are open through slots or openings at the peripheral surface or rim of the impeller disc to an annular liquid discharge chamber, circumferentially surrounding the rim of the. disc, from which chamber liquid is discharged via an outlet passage. Two difiuser rings are supported, respectively, in free-running sealing contact with opposite faces of the ice impeller disc over an annular area radially interposed between the two sets of axial through ports, to separate the stages and at the same time assist in supporting the disc against displacement from a rfixed plane of rotation.

The invention will be described in detail hereinafter, having reference to the accompanying drawings wherein FIG. 1 is a longitudinal elevational view of the pump, partially in section; FIG. 2 is an elevational view of the impeller disc and a portion of the drive shaft, to the same scale as in FIG. 1; and FIG. 3 is a sectional view through the impeller disc, taken on the line IIIIII of FIG. 2 and viewed in the direction of the arrowheads.

Referring to FIG. 1, the pump embodying the invention comprises a housing having two flanged housing sections 1 and 2 suitably held together by a plurality of bolts 3. Section 1 has a supporting base 4 provided with suitable holes 5, one of which is shown, to accommodate securing bolts. Section 1 has a central cylindrical portion having a stepped bore 6, successive portions of which provide a bearing surface for the drive shaft 7, a space for securing a packing gland 8, and tapped threads for receiving a suitable packing nut 9. A passage 10 provides communication to the packing gland for water lubricant from the chamber 11 in section 2 within which the impeller disc 12 is housed.

As will be evident from FIGS. 1 and 2, the impeller disc itself has a hub 13 with a stepped bore 14, into the smaller bore portion of which the inner end of the drive shaft extends with a close fit. A pin 15 extending diametrically through and press-fitted in aligned holes in hub 13 and shaft 7, serves to secure the impeller disc to the shaft in overhanging relation to the inner end of the shaft.

Section 2 has a central boss with a tapped bore 16 therein for receiving an inlet pipe 17. Tapped bore 16 opens into an inlet chamber 18 into which the corresponding end of the hub 13 of the impeller disc extends. Section 2 has formed therein an annular shoulder 19, the circular opening in which conforms closely to the outer diameter of the hub 13 so as to prevent direct entry of liquid from the inlet to the impeller disc chamber 11. Similarly, section 1 has an annular shoulder 20, the circular opening in which conforms closely in diameter to the outer diameter of hub 13, and which surrounds the end of the hub adjacent section 1. A plurality (illustratively shown as four in number) of axially extending drilled passages 21 through the wall of the hub 13 serves to provide pressure equalizing communication for portions of the chamber 11 at opposite sides of the impeller disc.

The impeller disc chamber 11 has a cylindrical outer wall 22 in which is formed a curved channel or groove which forms a discharge chamber 23. Chamber 23 communicates via a port 24 with the outlet port 25 which is tapped to receive a correspondingly threaded outlet pipe 26. As will be more fully apparent hereinafter, the outer peripheral surface or rim of the impeller disc 12 conforms closely, with appropriate clearance, to the diameter of the chamber 11. Also, the discharge chamber 23 is substantially symmetrical with respect to a plane midway between opposite faces of the impeller disc.

Two diffuser rings 27 and 28 are supported, coaxially of each other and of the hub 13 of the impeller disc, from the end walls of chamber 11 on housing sections 1 and 2, respectively. The rings are secured in place, as by welding, to a plurality of short pin-like bosses 29 formed on the housing sections and arranged circularly. The axial spacing between the diffuser rings conforms closely to the axial thickness of the impeller disc so that, in assembled condition, the opposite faces of the impeller disc engage the rings 27 and 28 in free-running sealing contact. The full purpose of the diffuser rings will be explained more fully later. It will be here noted, however, that they serve to assist in supporting the impeller disc for rotation in a fixed plane. The difficulties inherent in overhung impellers of heretofore-known centrifugal pumps are thus obviated.

Referring particularly to FIG. 2 and 3, the novel fea tures of the impeller disc will now be described. According to the invention, the impeller disc is constructed in a simple practical way of fabrication by providing an outer cylindrical tube 30, as suitable tubular member to form hub 13, and two circular cheek plates 31 and 32, of identical diameter. One of the cheek plates, illustratively shown as plate 31, is thicker than the other and is machined to provide four volute or spiral shaped recessess or passages 33, 34, 35 and 36 (FIG. 3) in one face thereof. A central hole 37 is then drilled or otherwise formed therein the receive the hub member. In addition, before assembly, the cheek plate 31 is provided with a pair of axially extending elongated slots 38, adjacent the outer end of the volute recesses 33 and 34 which are diametrically related, that is 180 with respect to each other Also, cheek plate 31 is provided with two relatively short slots 39 in diametral relation to each other at the inner ends of volute recesses 35 and 36, which are interposed between recesses 33 and 34 in 180 relation to each other. Cheek plate 32 is provided with a pair of similarly located elongated slots 40 and a pair of similarly located short slots 41.

To insure locking of the cheek plates against relative shifting rotarily when assembled in face-to-face relation, the two cheek plates are provided internally with suitably disposed aligned drilled holes for receiving dowel pins 42 therein.

Before assembly, the cylindrical tube is provided with two elongated slots 43 and 44 conforming in length substantially with the length of the outer opening of recesses and 36, respectively, and adapted to register therewith. Also, the tubular member for the hub is counterbored to provide the bore 14 and drilled to provide the axial passages 21. In addition, the wall of the hub is provided with two diametrally related short slots 45 and 46 for registry with the inner ends of volute recesses 33 and 34.

Upon assembly, the two cheek plates 31 and 32 are first placed together so that check plate 32 covers the recesses in cheek plate 31, with the dowel pins engaged in corresponding drilled holes in the cheek plates to lock them together in position such that the two elongated slots 38 in cheek plate 31 are in respective registry with the corresponding two elongated slots 40' in cheek plate 32. At the same time, the two short slots 39 in cheek plate 31 are in respective registry with corresponding short slots 41 in cheek plate 32.

With the cheek plates assembled as above described, they are inserted in the cylindrical tube 30 midway between the opposite ends thereof so that the tube extends an equal amount to either side of the assembled cheek plates. At the same time, the slots 43 and 44 in the tube 30 are located in registry with the outer ends of recesses 35 and 36, respectively. The tube is then welded or brazed to the cheek plates along the circular periphery of the cheek plates. In a similar manner, the tube forming the hub 13 is inserted through the central holes 37 in the two cheek plates so as to extend equally from opposite faces of the assembled plates. The tube is rotarily positioned in the holes 37 so that the slots 45 and 46 in the tube register, respectively, with the inner open ends of recesses 33 and 34. The tube is then welded or brazed to each cheek plate along the edge of the circular hole 37 in each cheek plate. This completes the assembly of the impeller disc 12.

Now let it be assumed that with the impeller disc secured to the stub portion of the drive shaft 7 by pressfitting the pin 15 through the hub 13, the shaft is inserted 4 through bore 6, packing gland 8 and packing nut 9, as shown in FIG. 1, until the outer face of cheek plate 31 contacts the face of diffuser ring 27. Housing section 2 may now be fitted to section 1 and the two sections bolted together, such that the face of diffuser ring 28 contacts the face of check plate 32.

Let it be further assumed that drive shaft 7 is connected to a suitable motive power source, such as an electric motor, and that suitable connections to the inlet pipe 17 and outlet pipe 26 are established for supply of liquid, such as water, to and delivery thereof from the pump.

Upon rotation of the impeller disc in the counterclockwise direction, as viewed in FIG. 3, the path of flow of the liquid through the pump is as follows: via inlet chamber 18, bore 14 of hub 13, slots 45 and 46 to recesses or passages 33 and 34; thence out through elongated slots 38 and 40 to the impeller chamber 11 outside the diffuser rings on both sides of the impeller disc; thence radially inward to the short slots 39 and 41, via which the flow is radially out through recesses 35 and 36 and the two slots 43 and 44 into discharge chamber 23, from which the flow is out through port 24 to the outlet pipe 26.

It will be seen that the arrangement of the volute recesses or passages and exit and entry ports therefor is such as to provide hydraulically balanced forces on the impeller disc, both for the initial stage (traversing passages 33 and 34) and the secondary stage (traversing passages 35 and 36). Moreover, it should be understood that variations in deliverly capacity and output pressure may be effected by variation in the lengths of the slots 43 and 44 in the cylindrical tube 30 of the impeller as well as by varying the lengths or widths of the slots 38, 39, 40 and 41 in the cheek plates. Also, the design of the impeller is such as to minimize, if not eliminate, the possibility of cavitation.

Having now described the invention, what I claim as new and desire to secure by Letters Patent, is:

1. A multi-stage centrifugal pump comprising the combination of a housing having an impeller chamber, an inlet port, an outlet port, and a drive shaft rotatably mounted in the housing, wherein the improvement comprises an impeller disc having a hub by which said disc is secured in overhung relation on the inner end of said drive shaft within said chamber, said impeller disc having four volute passages therein, a first two of which are in diametrical relation to each other and open at their inner ends to a bore in said hub in turn open to said inlet port, and a second two of which are in diametrical relation to each other and in quadrature to said first two passages, the outer ends of said second two passages being open at the periphery of said impeller disc, and thereby in communication with said outlet port, said impeller disc having also port means therein providing communication via said impeller chamber between the outer end of said first two volute passages and the inner end of said second two volute passages.

2. A multi-stage centrifugal pump, as claimed in claim 1, wherein the outer periphery of said impeller disc closely conforms in diameter to the internal diameter of the wall of said chamber, said housing having an annular groove in the outer wall of said chamber in radical registry with the outer openings of the said second two passages and constituting a discharge chamber communicating with said outlet port.

3. A multi-stage centrifugal pump, as claimed in claim 1, wherein said housing has a first annular shoulder closely surrounding one end of the hub of said impeller'disc and a second annular shoulder closely surrounding the opposite end of said hub to inhibit entry of liquid from said inlet port to said chamber.

4. A multi-stage centrifugal pump, as claimed in claim 1, wherein the hub of said disc has at least one axial pressure equalizing passage therein communicating the bore in said hub with the opposite end of said hub.

5. A multi-stage centrifugal pump, as claimed in claim 1, wherein the said port means in said impeller disc extend axially through said disc in intersecting relation to said volute passages, thereby providing communication from said volute passages to said chamber on both sides f said disc.

6. A multi-stage centrifugal pump, as claimed in claim 1, *wherein a pair of diffuser rings are supported on said housing within said chamber coaxially to said impeller disc and in spaced coaxial relation to each other such that said rings engage in free-running contact with opposite faces of said impeller disc over an annular area interposed between the port means for said first two passages and the port means for said second two passages.

7. A multi-stage impeller disc for use in a centrifugal pump, said disc comprising:

(a) a cylindrical rim,

(b) a pair of circular cheek plates of identical diameter conforming closely to the internal diameter of said rim and secured thereto in side-by-side relation, one of said cheek plates having a plurality of pairs of volute passages formed in the inner face thereof so as to provide hydraulic balance for liquid in said passages, said cheek plates having axial slots in axial registry with each other and communicating the outer end of each of a first pair of said passages with the outer faces of both of the said check plates, said check plates having also additional axial slots therein in axial registry with each other and communicating the inner ends of each of a second pair of said passages with the outer faces of both said cheek plates, each of said cheek plates having also a central circular opening therethrough in registry with each other, and

(c) a cylindrical hub extending through said central circular openings and secured to said cheek plates, said hub having ports communicating an internal bore thereof with the inner ends of said first pair of passages.

(d) said cylindrical rim having circumferentially spaced slots therein via which to communicate the outer ends of the said second pair of passages with the exterior of said rim.

8. A multi-stage impeller disc for a centrifugal pump, as claimed in claim 7, wherein locking means are provided for locking said cheek plates in fixed angular positions relative to each other.

9. A multi-stage impeller disc for a centrifugal pump, as claimed in claim 8, 'wherein said locking means comprises a plurality of dowel pins set partly in holes in one cheek plate and partly in holes in the other cheek plate.

10. A centrifugal pump having a housing providing an impeller chamber, and an impeller disc, as claimed in claim 7, mounted for rotation therein.

References Cited UNITED STATES PATENTS 1,666,257 12/1915 Rees 41598 1,346,796 7/1920 Rusher 41598 2,028,783 1/1936 Jacobsen 103--112 2,636,442 4/1953 Roth 1031 12 2,658,455 11/1953 Seinfeld 103-112 3,296,972 1/1967 Arkless et a1. 415211 HENRY F. RADUAZO, Primary Examiner US. Cl. X.R. 41553, 211 

